The reason for this activity is to get the students sense-making about the symbols from the context. We want them to feel that the course material is concrete and that the symbols we use hold meaning even from day one. We also want them to start feeling comfortable with the terminology and using it from day one. This also sets the stage for repeatedly showing the 6 postulates repeatedly through the course, both as a guide for what we have learned so far and where we're going within the course, and also as a chance to have them state deeper understanding about each postulate as the course progresses.